Hi its been a few years since I've been on this forum, but haven't had any problems with my 2004 Hemi Ram until last year when after lifter change my engine hits a wall above 4000rpm.

I decided 3 weeks ago since I finally had enough money and time to work on it to completely put an end to this problem once and for all! I threw the kitchen sink at it! I took both heads off and found NOT a single bent valve in the drivers side head or passengers side head. I lapped the valves & replaced a couple sketchy ones that had pitting and tested guides...all looked great! new valve seals in, new head gaskets & bolts ect. Camshaft lobes all measured within spec no rounding off or gouging. Put engine back together and the same thing...still hits a wall above 4000 rpm.

Video of it here:


Tests I've done:

First off I have a very free flowing exhaust with mid length headers & no catalytic converters on my truck and haven't for the last 3 years, have only had this issue for a year and truck has run great quite a long time without them!
Compression Test: All cylinders between 175psi to 190psi (not bad for a 202,000 mile motor!)
Fuel Pressure Test: 61psi (same fuel pressure as my 05 Hemi Durango that runs great)
OBD-2 O2 Sensor readings: Short term fuel Trim +/- 4% both bank 1 and 2. Long Term fuel trim bank 2 +/- 4%... (All good readings from the passengers side that had lifters replaced).
Long Term Bank 1: +15 (indicating lean drivers side bank, might be a vacuum leak since the number goes down below 10% with a rev) . If it were a fuel delivery issue or regulator & dirty filter I'd assume both banks fuel trims would be lean.
Idle Advance +8-10 at 650rpm
Vacuum Test: Steady 17-20 at idle no erratic bouncing or flutter looks like what you'd hope for in a vacuum test!
In a General OBD-2 scan only ONE CODE has come up and ONLY for a short time: a P0300 random multiple misfire code which was listed as a "pending code" not a current. Its since deleted itself from the pcm's log.
O2 sensors are doing their job via the scanner readings so no reason to change them.

Now for what parts I changed:

New Spark Plugs & Wires (tested all coils with a spark tester light and they all Fire)
Changed EGR
Swapped Throttle body (to a known good one)
New Cam sensor
New Crank Sensor
New Map Sensor
New intake Gaskets

Now I do have headers, but the fuel trims on the side that runs normal is well within spec for the pcm's tuning parameters.

The only things I have not changed are: Fuel injectors, IAT sensor & Engine temp sensors. I have a K&N Filter, have tested with and without it on the truck and it still does the same thing.

I'm nearly at wits end here as I know I have a motor that is testing good in all the major vitals, however the one thing that is off is the drivers side long term fuel trim which indicates a vacuum leak. Just not very sure how the heck I'd get a vacuum leak on just the drivers side without it affecting the passengers side fuel trim numbers.

Things I'm going to try next: Clean/and/or swap out injectors, put a new drivers side o2 sensor in incase its lying about its readings.

Any help would be great thanks!

 

I would be tempted to replace both O2 sensors..... NTK, or Denso please, skip bosch, they just don't work as well in these trucks.

Might try running some fuel injector cleaner thru it, see if that makes any difference at all, or maybe run premium gas for a tank or two. (or both?)

Check engine lite is on? What's it whining about? Is it just the random misfire?

What is fuel pressure doing when you are getting on it? (I think that is a parameter the PCM watches???)

 

I have post cat o2 sensors removed. Had them removed for at least 3-4 years with no problems since I installed headers. Its complaining about those. It ran great and I've reset my computer multiple times since this issue, even removed my Superchips tune and reinstalled to no avail. Might just end up putting on my spare fuel injector rail and/or my other intake manifold.

I took my stethoscope and listened to my injectors and they're all working, so maybe one is dirty or something. I'm 32 and I already have a few grey hairs from this. I'm a traveling mechanic for a living and wouldn't you know my own vehicle is the hardest to diagnose!

 

Try the non-fouler trick for the Rear O2 sensors. Works good on the second gens, (and the write up about them is in the 2nd gen faq section.) don't know if the 3rd gens are more picky. But, those codes 'shouldn't' have much/any effect on how the truck runs. (I don't think.....) The rears are just cat monitors in any event.

Just because they are ticking, does not necessarily imply they are injecting. Might try a power-balance test. Disable IAC, (or electronic throttle, as the case may be.) and then take out one cylinder at a time. (disconnect coil, or injector) Monitor how much RPM drop you get on each cylinder, and see what the numbers look like.

 

Thanks for your help! Unfortunately every day a new test a new square one

I rigged up 2 feet of fuel injection hose to extend my fuel pressure gauge and took it for a drive, went from 61psi at idle down to 58 under full throttle. Hardly the smoking gun I was looking for. Then I did the power balance test and used the injector connectors instead of the coils because of being dual plug per cylinder the injectors were easier. Only cylinders 7 and 8 barely made a difference but they did, still no definitive new direction to explore. I think I'll clean injectors tomorrow and try it again.

So far I compared my idle advance to my 05 Hemi Durango and my Ram is at 9 degrees and the Durango that runs perfect does 12-15 degrees at the same idle rpm. That within the margin?

 

Can't hear the video, my speakers aren't working this morning... Have you tried looking at the ODB2 system while its running/driving? I was pretty impressed what you can get out of the system with the bluetooth units with the torquePro android app. I'd be interested in seeing the timing profile through the rpm range.

Not the one I have, but similar...

Edit:
Got my speakers working, that sounds like a rev limiter.

 

maybe your cats are getting clogged, drop exhaust and see if that helps

 

I don't have any cats on the truck. 3 inch dual exhaust from mid length JBA headers. Pretty much as free flowing as it gets.

 

I was initially laughing when people brought this up, but you may be on to something....

Makes me wonder, exactly what system tells the pcm the motors rev limiter that its out of park? The trans solenoid pack/shift mech/electronics assembly right? Maybe the pcm thinks the truck is still in park somehow and keeps that rev limiter. Maybe this whole time I've been scrutinizing the engine and its electronics and its really the solenoid pack in the trans causing all this trouble? Seriously I've actually had issues with this solenoid pack and having to restart the engine to get overdrive back a few times, as well as this trans acting like its in 3rd gear from a stop. Lately I've had zero problems with the trans, however I did have legit problems with the solenoid pack and I know those just don't cure themselves. I've been meaning to change that, however wanted to get the engine sorted first! I would completely die laughing if this was it the whole time! It would really make sense as to why no codes are popping up!.

As for timing, pretty much at idle its bounces from 7-10 degrees with an average of 9 and as soon as I moderately touch the gas for cruising its between 24-28 degrees and full throttle 36 degrees for a high. Nearly identical to what my Hemi Durango that runs perfect does, from watching while I drive the differences are barely any. My Hemi Durango does however have a bit more timing at idle 10-15 degrees it bounces between, but averages 12 degrees. Truck does have headers, 3 inch exhaust and an intake which may affect how the pcm compensates for timing and the differences between the two.

 

A decent scanner should be able to tell you what gear the PCM thinks you have it in. Not sure if that would be your problem, (it would make sense....) as I would expect the pcm to complain about it, while it was also shifting gears...... See a speed other than zero in park would most certainly be confusing.